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Among older adults, CKD was associated with excess mortality risks that are as high as or higher than the excess risks among middle-aged adults.

SAN DIEGO -- Both a low estimated glomerular filtration rate and high albuminuria are associated with end-stage renal disease and death at all ages and are not just part of the aging process, researchers found.

In a large cohort study, relative mortality risk for reduced eGFR was higher in every age category, but fell with increasing age (P<0.05), with similar albeit less evident findings for increased albuminuria, Josef Coresh, MD, PhD, of the Chronic Kidney Disease Prognosis Consortium Data Coordinating Center in Baltimore, and colleagues reported online in the Journal of the American Medical Association.

Absolute risk differences were higher at older ages.

The findings will also be presented at the American Society of Nephrology meeting in San Diego later this week.

Some researchers have suggested that kidney disease risk assessment be based on eGFR and albuminuria levels, although it's been unclear as to whether chronic kidney disease (CKD) represents a true disease or whether loss of eGFR is just a part of the natural aging process.

To assess the potential interaction of these parameters with age, the researchers conducted a meta-analysis of 2,051,244 patients from 33 general population or high-risk cohorts and 13 CKD cohorts from Asia Australasia, Europe, and North and South America. Mean age was 50 and mean follow-up was almost 6 years.

There were 112,325 deaths and 8,411 ESRD events during that time.

Overall, Coresh and colleagues found that death and ESRD risks were higher at lower eGFR and higher albuminuria in every age category.

The age interaction with albumin-to-creatinine ratio (300 mg/g versus 10 mg/g) was less evident, but followed a similar pattern -- although it was only significant for ages 65 to 74 and for those 75 and up (P=0.02 and P=0.002, respectively):

18 to 54: HR 2.53, 95% CI 2.13 to 3.03

55 to 64: HR 2.10, 95% 1.84 to 2.88

65 to 74: HR 2.10, 95% 1.83 to 2.44

75 and up: HR 1.73, 95% CI 1.45 to 2.05

And again there were similar trends in absolute risk differences for high albuminuria, with the following amount of excess deaths per 1,000 person-years:

18 to 54: 7.5

55 to 64: 12.2

64 to 75: 22.7

75 and up: 34.3

The researchers noted that all findings were similar for subgroups with CKD and ESRD.

They concluded that the findings suggest kidney measures used for defining and staging CKD are strong predictors of clinical risk across all ages.

"This contradicts concerns raised by some that current CKD guidelines should be used with caution in older individuals and that low eGFR reflects only natural aging," they wrote.

The findings also support recommendations from several groups that CKD measures should be added to mortality risk equations, they added.

And the strong increase in mortality seen at older ages suggests that older adults "should not be left out of management strategies of CKD."

The study was limited by concerns about the validity of the CKD-EPI equation in older patients, by heterogeneity across cohorts, and because there is no internationally accepted gold standard for measuring urine albumin.

In an accompanying editorial, Ian de Boer, MD, of the University of Washington in Seattle, affirmed that clinicians should recognize older adults with CKD as being at higher risk of death.

"All efforts should be made to apply treatment strategies that are proven effective for the primary or secondary prevention of cardiovascular disease in this population and are appropriate to the individual," de Boer wrote.

"These data," he added, "combined with the knowledge that CKD is more prevalent with advancing age, identify older adults as a population for which CKD has exceptional individual and public health importance."

The study was supported by the National Kidney Foundation, whose funding sources include Abbott and Amgen.

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